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Fired Equipment
FALL: Trip failed to operate as flow meter was frozen. 2 tubes burst, caught fire and damaged the rest. Heat trace such instruments in cold weather. WWW
HDS Catalyst regeneration: Insufficient coil flow maintained led to tube rupture. Provide coil inlet FAL + outlet FALL
FALL: had 5 minutes time delay during start-up. Operators added a field delay, thinking it is not sufficient. Flow reduction caused by feed pump trip. Tube rupture, hydrocarbon into firebox and fire
RV at furnace inlet popped due to restriction downstream. FALL to shut fuel supply was upstream of RV. Overheated furnace tubes burst. WWW
Glycol reboiler: Oil carried with fuel gas leaked onto hot surface. Fire. Avoid skimmer flash gas as fuel gas to avoid liquid carry over. Trip fuel gas on skimmer LAH and oil build-up in gas supply lines. Fuel Gas KOD should be generously sized to avoid liquids from source vessels/ condensation enroute
Glycol reboiler: Light ends carry over to Glycol contactor caused foaming in contactor. Paraffin plugged column packing impeded condensate drain into reboiler. Condensate in vent gas ignited by hot flue gas stack
Low FD Fan stack intake height can lead to leaking hydrocarbon suck-in with air. Destroyed many heaters and boilers. LNG Train exploded
Failure to purge before a light-up and after a failed light up has resulted in many explosions. Killed many
Purging: Critical if H2 is in the fuel gas. Low molecular weight gas can easily leak into the firebox during shutdown. Wide flammability range. BP
Boiler: One of the 2 burners was shut-off without adjusting the draft. The second burner went off. Fuel gas was shut at the supply line and not at the burner. After opening the main valve for relighting, accumulated gas in the firebox exploded. BP
Light-up: After a trip, due to SDV leak, some fuel oil + inventory downstream of SDV may drain to firebox. Due to high flash point, it may not be detected by gas detectors used before relighting the burners. Explosion. Purge before relighting and use constant burning pilots. WWW
Low NOx: Unstable flame. Operator manually adjusted air. After a puff the heater exploded. Always increase air before increasing fuel; and reduce fuel before reducing air
Low NOx: Reboiler retrofitted with low NOx burners. Burners kept plugging with coke and iron oxide creating unstable flames. Efforts to correct flame instability through damper and air register adjustments appeared unsuccessful. Fuel gas cloud in firebox. Explosion. BP
Fuel change over: From oil to gas or vice versa. Attempt to maintain a stable gas flame until oil flame is stable led to air starvation and explosion. Maintain total firing and excess air
Fuel change over: From low to high Mol Weight Gas. Before burner pressure was trimmed by temperature controller, excess fuel resulted in firebox explosion
Fuel change over: High Sulphur fuel oil in a heater designed for low Sulphur oil. Furnace 25Cr-20Ni or 25Cr-12Ni supports failed in a high Sulphur + Vanadium and Sodium environment. BP
Fuel change over: High Sulphur fuel oil in a heater designed for low Sulphur oil. Acid gas corrosion of piping below acid dew point. High Vanadium and Sodium in fuel can attack tube supports
Fuel Rich. Plant backend trip with rapid depressurization of Synloop led to rapid purge gas loss to fuel system. As the makeup Natural Gas to Fuel Drum PCV set point was not lowered in time, rich fuel gas - 3 times normal LHV - overfiring caused high convection coil outlet temperature, COT. Operator mistakenly reduced combustion air, realized the mistake and reintroduced air in a fuel rich environment. Mild internal explosion shook and damaged reformer brickwork, catwalks grating etc. Add feed forward controls on Natural Gas make-up flow (Scott Newton)
Reformer: Cable failure caused counterbalance weight to fall and rupture a 1” naphtha: steam nozzle. Ensure that cables don’t swing and backup safety system are working. Inspect regularly. BP
Steam Cracker: Tube support hanger failed and fell onto a maintenance contractor as the tubes were removed. Cracks in support hangers should be checked first during maintenance. BP
Reformer: Flame impingement from a leaky tube or blocked burner tip. Tube failure by SCC (Stress Corrosion Cracking) in the HAZ (Heat Affected Zone)
Reformer: Tubes ruptured near bottom at 10% firing due damaged catalysts blocking pig tails
Reformer: 54 tubes failed. Site changes - shortening pig tails that increased stress
Reformer: Start-up. Sudden vaporization of trapped water in tubes caused pressure surge; destroyed 5 tubes, whose splinters destroyed rest of the 41 tubes. Heat slowly. Steaming out requires caution
Tube Material: Changed from 5Cr-½ Mo to CS as a quick measure and forgotten. Section failed. BP
Decoking: Bottom connection at the inlet. Water collected above the valve and froze in cold weather. Line ruptured allowing furnace feed leak. WWW
Visbreaker. N2 was used to purge and gas free vertical hairpin coils. Gas oil accumulation in the tube bottoms (legs), trapped the N2. When a top plug header was removed, it ejected. Injury. BP
Start-up. Gas was introduced into reformer hot tubes running with steam only during a hot restart. Resultant thermal shock ruptured the tubes (Scott Newton)
Start-up: Establish equal flow in all passes and heat slowly. Potential vaporization and unequal flow in passes resulted in a few radiant tubes cracking. Resultant firebox flame destroyed another coil
Start-up: Heat slowly. Steaming out moisture in refractory/ insulation requires attention
Stack in-situ Oxygen (Zirconium Oxide) analyzer with electrical heater to keep element above auto-ignition temperature of unburnt fuel (=700°C). Its flame arrestor may degrade. C2= furnace damaged
Incinerator: Do not externally insulate hot casing of firebox. Casing got red hot and failed. Use Personnel Protection Mesh instead
Incinerator: Inadvertent water addition into methyl mercaptan caused hydrate blockage in winter. Operators cleared it by spraying hot water on the piping and venting to an incinerator. Resulted in PAH in the vent line to incinerator in another part of the plant. Operators there assumed liquid blockage in their line and drained it. Liquid mercaptan drained, vaporized. 24 tons released. Fatalities
Hydrate forming chemicals: CO2, H2S, Cl2, C1, C2, C2=, Acetylene, Methyl Mercaptan, Vinyl Fluoride, Natural Gas, and other Hydrocarbon gases
Incinerator: 2 incidents in Phthalic Anhydride (PA) plant incinerators. (1) Feed gas preheated by flue gases. Internal rockwool insulation in the feed duct was soaked up with PA. Explosion. Duct work replaced with SS piping with external insulation (2) PA accumulating at the inlet of Feed Preheater (Recuperator) moved thru it during start-up and exploded at the outlet
Incinerator: Explosions. (1) Combustibles accumulation in the feed drum during start-up resulted in an explosion at the outlet of Start-up Air blower (2) While switching from Caustic Scrubber back to Incinerator, incinerator hot gases travelled via a leaking valve to feed gas to Caustic Scrubber
Incinerator: Outlet temperature from a catalytic incinerator burning ethyl acrylate, shot up. Flame flash back and explosion in upstream plant. Failure of temperature alarm and trip
Incinerator: Oil fumes were routed to an incinerator via flame arrestor. An emergency bypass to incinerator outlet without flame arrestor provided, allowed flame flash back to upstream plant. Fire and explosion. Failure of temperature alarm and trip; Poor design
Incinerator: Residual resinous materials accumulation in the feed duct exploded
Incinerator: To burn H2, NH3 and Pyridine stream. Potential blockages in a perforated plate below ceramic bed. Explosion
Coal fired boiler: Clinkers formed and bridged / blocked ash outlet, that led to ash build-up and firebox pressure build-up. While rodding out the clinkers, firebox high pressure trip was bypassed. Resulted in firebox pressure fluctuation. Unburnt coal particles were carried into convection/ economizer section that resulted in secondary combustion and high temperature. Blast in the economizer resulted in hot gas, steam and ash release. Burn injury to 300 odd persons
Boiler: While taking down a boiler for annual maintenance, remaining fuel gas was purged to the firebox. A spark from the Electrostatic Precipitator installed upstream of stack ignited it. Explosion. BP
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